1. Field of the Invention
The invention relates to non-impact printer apparatus and methods and, more particularly, to apparatus and methods for recording on a medium that is moving at a variable rate.
2. Description Relative to the Prior Art
In the prior art, non-impact printers are known for recording on a suitable media. Examples of such printers are light-emitting diodes, thermal printers, ink jet printers, etc. Examples of media for recording may be a photoconductor, photographic film, thermal recording paper or plain paper such as for ink jet.
In printers using light-emitting diodes (LED's) printheads to record, a series of LEDs are arranged in a column perpendicular to the direction of travel of the recording medium which say is photographic film. For each line of pixels to be recorded in the main scan direction, i.e., direction perpendicular to direction of film movement, a control signal is developed within the controlling circuitry supporting the printhead to synchronize the recording of this line or column of pixels. Such a control signal may be generated in response to an encoder or perforation sensor or other signal generator device detecting displacement of a fixed amount of movement of the film. In forming images of characters on the film, it is important that the amount of exposure for each pixel be appropriate even though the speed of the medium is changing. It is also important in printing characters to avoid gaps between adjacent lines of pixels in the sub-scanning direction. Such gaps may provide difficulty in reading of images on the film by automatic image readers.
It is, therefore, an object of the invention to provide a non-impact printer apparatus and method that is highly suited for recording with a medium that is moving at a variable rate.